1. Field of the Invention
The present invention relates to a method for performing a non-invasive blood gas test, and more particularly to a blood gas testing method that utilizes a venous blood sample together with a pulse oximeter and a plurality of mathematical equations.
2. Description of the Prior Art
A blood gas test measures the amounts of oxygen and carbon dioxide in the blood and determines the acidity of the blood. This test is also commonly known as arterial blood gas analysis. Unlike most other blood tests, for which samples are drawn from a vein, the blood gases sample is taken from an artery, usually in the wrist, groin, or arm. The site is cleaned and disinfected; then a local anesthetic is injected. Once the area is numb, a needle is inserted into the artery and a sample of blood withdrawn into a special syringe that prevents contamination by outside air. After the sample is drawn, pressure must be applied to the site for 5 to 15 minutes to prevent bleeding. Blood gas measurements, performed by trained personnel, are usually carried out in a hospital, emergency room, or large laboratory setting. The analysis must be done immediately following sample collection; and specialized equipment is required.
Prior art teachings have disclosed various methods and techniques for acquiring blood gas data, or have related to blood gases more generally. Such examples can be found at: U.S. Pat. Nos. 3,224,436; 3,638,109; 3,874,850; 4,109,505; 4,114,604; 4,163,734; 4,321,545; 4,353,867; 4,493,692; 4,512,348; 4,786,394; 5,061,631; 5,526,809; 5,533,512; 5,577,499; 5,603,817; 5,788,631; 5,976,085; and 6,096,275; U.S. Pat. Publication Nos. 2002/0087057; 2003/0000833; and 2003/0060727; Foreign Patent Publication Nos. IT 1233172; JP 08182665; JP 11056824; RU 2105980; WO 03063697; WO 9001896; and WO 9806332; and the following scientific articles “The accuracy of calculated base excess in blood” at Clin Chem Lab Med. 2002 April; 40(4):404-10; “The van Slyke equation” at Scand J Clin Lab Invest Suppl. 1977 January; 37(146):15-20; “Simultaneous measurements of blood pH, pCO2, pO2 and concentrations of hemoglobin and its derivatives—a multicenter study” at Scand J Clin Lab Invest Suppl. 1990; 203:75-86; “A proposal for analyzing the acid-base balance at steady state in vivo” at Adv Exp Med Biol. 1998; 454:29-34; and Chemical Principles, 6th edition 1985 by CBS College Publishing. 1981. However, none of these references disclose or suggest a method for performing a non-invasive blood gas test that utilizes a venous blood sample together with a pulse oximeter, and a few specific mathematical equations (as disclosed hereinbelow) to safely determine the following data points of the blood sample: (i) the pH level; (ii) the [H+] concentration; (iii) the [HCO3—] concentration; (iv) the partial pressure of carbon dioxide; and (v) the oxygen saturation level.
Because the blood sample is taken from the artery, a patient undergoing a traditional arterial blood gas test experiences more pain and discomfort than other blood tests that instead utilize venous blood samples. There remains a need in the art for a method for performing a non-invasive blood gas test. In particular, there remains a need in the art for a method for performing a non-invasive blood gas test that (i) does not require an arterial blood sample, but instead uses a venous blood sample; (ii) does not require the use of special machines to analyze a blood sample to give the gas levels of the blood; (iii) is less painful to the patient; (iv) is safe for the patient; and (v) generates fast results.